Gonorrhea: It’s what’s for dinner

When people discover I don’t eat meat, the follow-up question is standard: ‘Why?’

One of the most common guesses is health, for the typical litany of meat-related health risks: cholesterol, heart disease, obesity, and the like. I imagine my interrogators aren’t thinking of gonorrhea – but that answer might be considerably closer to the truth.

“This organism has basically been developing resistance against every medication we’ve thrown at it,” said Dr. Manjula Lusti-Narasimhan, a scientist in the [WHO]’s department of sexually transmitted diseases. This includes a group of antibiotics called cephalosporins currently considered the last line of treatment.

Once considered a scourge of sailors and soldiers, gonorrhea – known colloquially as the clap – became easily treatable with the discovery of penicillin. Now, it is the second most common sexually transmitted infection after chlamydia. The global health body estimates that gonorrhea is responsible for some 106 million infections annually.

Gonorrhea is hardly the first infectious disease to acquire antibiotic resistance. The mechanism – natural selection – is relatively straightforward: the bacteria that survive antibiotic treatment due to resistance-conferring genetic mutation will pass those genes on to their offspring.

Furthermore, it is not a recent discovery. In a 1945 interview with The New York Times – the year that penicillin became available to the public – Alexander Fleming cautioned that the inappropriate use of antibiotics would lead to the propagation of resistant bacteria. When antibiotics are necessary to treat humans, they place caretakers in something of a Catch-22: sure, you can refrain from using them to protect their effectiveness, but then what’s the point of not using them? Fleming urged a cautionary approach, and suggested that penicillin be used only when necessary, only in sufficient quantity, and only for sufficient duration so as to completely eliminate resistant strains.

But where resistance in some bacteria, like Methicillin-resistant Staphylococcus arueus (MRSA), can be largely ascribed to over-prescription of antibiotics, or the failure of patients to self-administer them correctly, gonorrhea is thought to pick up resistance from bacteria it encounters in the wild – and the source of those ‘wild’ bacteria is no great mystery.

In 1949, Dr. Thomas Jukes, an employee of American Cyanamid, was experimenting with antibiotic use in agriculture. Antibiotics were already used to treat sick animals, but Jukes’ work led to a startling discovery: when he mixed subtherapeutic levels of tetracycline into the feed of healthy animals, they experienced a spectacular increase in growth.

Today, a full 90% of antibiotics used on farms are fed to animals subtherapeutically. Meanwhile, the total amount of antibiotics fed to farm animals has increased exponentially, rising from approximately half a million pounds by weight in the mid-1950s to just over a million in 1960, and reaching an estimated 24.6 million pounds in 2001. To put the amount under discussion in some perspective, the antibiotics used to treat sick humans in 2001 amounted to a measly three million pounds.

The consequences of this practice are predictable. Tetracycline, an antibiotic commonly fed subtherapeutically to livestock, provides an instructive example. The drug is not degraded by resistant bacteria, but simply expelled from the cell, into the bloodstream, and ultimately into the environment. Because of the molecule’s relative stability, it persists for a long time and continues to select for bacterial resistance. Tetracycline has been recovered from soils plowed with animal feces, as well as human municipal water supplies in both the United States and Europe.

When first introduced to the livestock industry, 5-10 parts per million (ppm) of tetracycline was sufficient to stimulate growth in cattle. Today, 50-200 ppm is necessary to achieve the same effect. It is tempting to believe that resistance is only a problem for the farmers who must buy ever-increasing quantities of tetracycline, but antibiotic resistance is hardly confined to the farm: a full 75% of the antibiotics fed to livestock pass into their surroundings.

In other words, antibiotics have become an ambient feature of the environment, where they raise the general level of resistance within the microbial community.

In one 2008 study, researchers tested eleven soil samples from distinct locations and discovered in each strains of bacteriathat could survive eating nothing other than the compounds intended to destroy them. The antibiotic-eating bacteria – including Shigella flexneri, which causes diahrrea, and E. coli – hailed from eleven distinct orders of bacteria, and each of the eighteen antibiotic staples tested by the scientists could be digested by at least one species. The bacteria were able to survive in concentrations of antibiotics greater than one gram per liter, which is fifty times above the minimum level that typically defines antibiotic resistance.

And to make matters worse, bacteria would make excellent kindergarteners: they are very good at sharing.

Like any eukaryotic cell, bacteria have chromosomes. However, bacteria are unique in that they can also harbor plasmids, small circles of DNA that exist separately from chromosomal DNA. By traveling through a physical connection called a pilus, these plasmids can move not only between bacteria of the same species but between bacteria of unrelated species. In fact, plasmids are often made up of DNA spliced together from many different species to create a single transferable block of nucleic acid.

The existence of plasmids means there is no barrier between the bacteria harbored inside humans and those that inhabit livestock and the wider world. The gene pools are one and the same. And this fact is likely to play no small part in gonorrhea’s ability to acquire antibiotic resistance. Back to the AP:

Scientists believe … the gonorrhea bacteria’s astonishing ability to adapt means the disease is now close to becoming a super bug. Gonorrhea is particularly quick to adapt because it is good at picking up snippets of DNA from other bacteria.

In an environment awash in antibiotics, those other bacteria are all likely to harbor resistance to at least one antibiotic. Unsurprisingly, the list of drugs to which the ‘gonorrhea superbug’ is already resistant includes penicillin and tetracycline.

And here we run up against the underlying issue, which is that modern husbandry is literally dependent on antibiotics. The increased growth the drugs provide is crucial to maintaining beef producers’ slim profit margins. Meanwhile, Concentrated Animal Feeding Operations (CAFOs) – where today’s cattle are fattened on a diet of unfamiliar foods – are built to contain as many livestock as possible. Where subtherapeutic antibiotics were introduced to stimulate growth rates, they are now indispensable agents of disease control.

The WHO report skirts around this issue: a scan of the report turns up exactly zero instances of the terms ‘farm’, ‘animal’, ‘subtherapeutic’, or other related search terms. Its core recommendations focus almost exclusively on treatment and prevention of the disease, a valuable contribution, but one that does not engage the underlying causes of resistance development:

advocacy for increased awareness on correct use of antibiotics among healthcare providers and the consumer, particularly in key populations including men who have sex with men (MSM) and sex workers

effective prevention, diagnosis and control of gonococcal infections, using prevention messages, and prevention interventions, and recommended adequate diagnosis and appropriate treatment regimens

systematic monitoring of treatment failures by developing a standard case definition of treatment failure, and protocols for verification, reporting and management of treatment failure

effective drug regulations and prescription policies

strengthened AMR surveillance, especially in countries with a high burden of gonococcal infections, other STIs and HIV

capacity building to establish regional networks of laboratories to perform gonococcal culture, with good-quality control mechanisms

research into newer molecular methods for monitoring and detecting AMR

So while the WHO Report on antibiotic-resistant gonorrhea skirts the role of livestock, it has at least given me the opportunity to point out the industry’s success in externalizing much – if not most – of the true cost of its harmful practices. Yes, ceasing to administer antibiotics to livestock at subtherapeutic levels would raise the price of meat. It would also bring the price meat better into line with its true cost.

So if you’re ever fortunate enough to experience that burning sensation while ‘going about your business’, please remember: it’s just the cost of doing business.